Thermoelectric coolers include a matrix of thermoelectric couples formed of n-type and p-type semiconductor material. The thermoelectric couples are connected electrically in series and thermally in parallel. The thermoelectric couples are sandwiched between two ceramic plates. The two ceramic plates define either the cold side or hot side depending on the connection of the dc voltage. With a positive dc voltage applied to the n-type thermoelement, electrons pass from the p- to the n-type thermoelement and the cold side temperature will decrease as heat is absorbed. Cooling is proportional to the current and the number of thermoelectric couples, and occurs when electrons pass from a low energy level in the p-type thermoelement to a higher energy level in the n-type thermoelement. The heat is then conducted through the thermoelement to the hot side, and liberated as the electrons return to a lower energy level in the p-type thermoelement. To keep the device working, it is necessary to remove the heat dissipated at the hot side. Thus, a heat sink is attached to the hot side for heat removal. The thermoelements are hereinafter referred to as "legs".
Prior thermoelectric coolers have been fabricated using flat conductive tabs stamped from strips of conductive metal preferably copper. Each tab has a size sufficient to receive ends of a pair of legs in a spaced relationship.
The tabs are placed in a grid type mold by placing the tabs on the grid and brushing the grid in a manner to orient the tabs for grid acceptance. A ceramic plate is then screen printed with a solder paste. The grid with tabs is then pressed against the solder paste portions of the plate. The tabs stick to the ceramic plate and the grid removed. The tabbed ceramic plate is then placed in a furnace to reflow the solder to substantially permanently attach the tabs to the ceramic plate. Two grids are used. A first type grid contains the hot side pattern and the second type grid contains the cold side pattern. A solder flux is then applied to the tabs of the tabbed ceramics. A leg matrix mold is then filled with legs by vibrating the legs into the mold. The filled mold is then aligned with the solders fluxed tabs of a first one (either the hot or cold side) of the tab patterned ceramics and pressed into the solders flux. The leg matrix mold is then removed and the legs permanently attached to the tabs by reflowing the solder. To complete the thermoelectric couple the opposing ends of the legs are similarly attached to the patterned tabs of a second one (either cold or hot as appropriate) of the tab bearing ceramics.
A problem with the existing thermoelectric cooler is its cost. The complexity of the elements for the component parts of the thermoelectric cooler dictates that considerable manual labor be expended in the process for assembling the elements for machine combination into components, and assembling the components for machine combination into thermoelectric coolers.